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MIT OpenCourseWare http://ocw.mit.edu 5.111 Principles of Chemical Science Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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21.1 5.111 Lecture Summary #21 Acid-Base Equilibrium Read Chapter 10 Topics: Classification of Acid-Bases, Autoionization of Water, pH Function, Strength of Acids and Bases, Equilibrium Involving Weak Acids. Classification of Acids and Bases 1. Arrhenius - a narrow definition of acids and bases An acid is a substance that when dissolved in water increases the concentration of hydrogen ions. A base is a substance that increases the hydroxide concentration. 2. BrØnsted-Lowry - a broader definition A BrØnsted-Lowry acid - a substance that can donate a hydrogen ion A BrØnsted-Lowry base - a substance that can accept a hydrogen ion Example 1 CH 3 COOH (aq) + H 2 O (l) H 3 O + (aq) + CH 3 COO - (aq) Acid1 Base2 Acid2 Base1 (note: hydronium ion H 3 O + (aq) is used instead of H + (aq) to represent the true nature of hydrogen ions in water) Acid-bases occur as conjugate acid-base pairs . CH 3 COOH and CH 3 COO - are a pair. H 2 O and H 3 O + are a pair. The conjugate base of an acid is the base that is formed when the acid has donated a hydrogen ion. The conjugate acid of a base is the acid that forms when base accepts a hydrogen ion. Example 2 Which are BrØnsted-Lowry acids and which are BrØnsted-Lowry bases? - HCO 3 (aq) + H 2 O (l) H 3 O + (aq) + CO 3 -2 (aq) - HCO 3 - (aq) + H 2 O (l) H 2 CO 3 (aq) + OH (aq) amphoteric - molecules that can function either as acids or bases depending on the reaction conditions.
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21.2 3. Lewis Acid and Base - more general definition - applies to reactions that don't involve a hydrogen ion Lewis base - species that donates lone-pair electrons
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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lecnotes21 - MIT OpenCourseWare http/ocw.mit.edu 5.111...

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